Code generating apparatus, reference signal generating apparatus, and methods thereof

ABSTRACT

A code generating apparatus, demodulation reference signal generating apparatus, and methods thereof. The demodulation reference signal generator includes generating a non-correlation sequence for RS of a first resource block; spreading spectrums of elements in the non-correlation sequence for RS to be mapped to a first frequency resource of the first resource block, by using a first group of codes; second spreading spectrums of elements in the non-correlation sequence for RS to be mapped to a second frequency resource of the first resource block, by using a second group of Codes; the first and second frequency resources are adjacent frequency resources in frequency resource elements used for RS transmission in the first resource block, and the first and second groups of Codes are mirrors in column to each other; and mapping the spectrum-spread elements to the first and second frequency resources, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 13/544,475, filed onJul. 9, 2012, now pending, which is a continuation of InternationalApplication No. PCT/CN2010/070087, filed on Jan. 8, 2010 in The People'sRepublic of China, the entire contents of each are herein whollyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to transmission technologies in thewireless communication system, and more particularly, to a codegenerating apparatus, a reference signal generating apparatus, andmethods thereof used in Long Term Evolution and Long TermEvolution-Advanced systems.

BACKGROUND OF THE INVENTION

The Long Term Evolution-Advanced (LTE-Advanced) next-generation wirelesscommunication system of 3GPP requires the downlink to provide a peakrate of 1 Gps and a peak spectral efficiency of 30 bps/Hz, and thisbrings about challenges to the physical layer transmission scheme of thesystem. A multiple input multiple output (MIMO) multi-antenna systemsupports transmission of parallel data streams, thereby greatlyenhancing the system throughput. Under general circumstances,independent forward error-correcting code encoding is firstly performedin parallel data streams transmitted in the multi-antenna system, andthe encoded codeword is then mapped to one or more data transmissionlayers. When the codeword is mapped to plural transmission layers, itsuffices to convert the serial data output from the encoder intocorresponding plural layers. In one transmission, the number of alllayers supported by the system is also referred to as the rank of thetransmission. The process of converting the data of each layer into thedata of each physical antenna is referred to as the pre-coding processof signals. LTE-Advanced Rel-10 supports the pre-coding technique withthe maximum rank of 8.

In order for the receiving terminal to perform MIMO decoding and theassociated demodulation, it is necessary for the transmitting side totransmit a pilot sequence, namely a demodulation reference signal(hereinafter referred to as “DMRS”), for estimating channels. Design ofDMRSs requires that corresponding DMRSs of data transmission layers beorthogonal to one another, that is, to ensure that equivalent channelsto the pre-coded channels of the transmission antennas are free ofinterference. In the Rel-10 system, corresponding DMRSs of the datatransmission layers are differentiated by the frequency divisionmultiplexing (FDM) and/or code division multiplexing (CDM) mode(s). Codedivision multiplexing is realized by spectrum-spreading sequences withideal correlation via an orthogonal cover code (hereinafter referred toas “OCC”) sequence. The OCC sequence is usually a Walsh sequence or adiscrete Fourier transform (DFT) sequence.

As the inventors found during the process of the present invention, ifan OCC sequence is mapped (spectrum-spread) in a time domain, it isusually presumed that channels on the physical resources correspondingto the cover code sequence are identical. Assume that the spread factorof a spectrum-spread sequence is M, it is then considered that channelresponses of M number of OFDM symbols are identical. Such assumption istrue only in a low-speed motion environment. With the increase in motionspeed of a mobile station, the change in channel responses of the Mnumber of OFDM symbols accordingly increases, and orthogonality of thespectrum-spread code is damaged, whereby data transmission layersinterfere with one another, and the precision in channel estimation islowered.

Moreover, in the Rel-10 system, DMRSs are subjected to the samepre-coding treatment as the data, and mapped to transmission antennas.The pre-coding treatment enables the DMRSs corresponding to thecode-division multiplexed data transmission layers to be linearlystacked, and when DMRSs corresponding to M number of data transmissionlayers are stacked in the same direction, a signal with an amplitude ofM is obtained; whereas when DMRSs corresponding to M number of datatransmission layers are stacked in opposite directions, they counteractone another to obtain a signal with an amplitude of zero. If such powerimbalance of each transmission antenna occurs in the entire frequencydomain bandwidth, efficiency of transmission power will be markedlylowered.

As should be noted, the above introduction of the background ispresented merely to facilitate clear and comprehensive explanation ofthe technical solutions of the present invention, and to make it easyfor persons skilled in the art to comprehend. It should not beconsidered that these solutions are publicly known to persons skilled inthe art only because they have been enunciated in the Background of theRelated Art section of the present invention.

Reference documents of the present invention are listed below and hereinincorporated by reference, as if they were described in detail in theDescription of the present application.

-   1. [Patent Document 1]: Hooli Kari, Pajukoski Ka, et al., Method,    apparatuses, system and related computer product for resource    allocation (WO 2009056464 A1)-   2. [Patent Document 2]: Che Xiangguang, Guo Chunyan, et al.,    Variable transmission structure for reference signals in uplink    messages (WO 2009022293 A2)-   3. [Patent Document 3]: Cho Joon-young, Zhang Jianzhong, et al.,    Apparatus and method for allocating code resource to uplink ACK/NACK    channels in a cellular wireless communication system (US 2009046646    A1)-   4. [Patent Document 4]: Yang Yunsong, Kwon Younghoon, System and    method for adaptively controlling feedback information (US    20090209264 A1)-   5. [Patent Document 5]: Pajukoski Kari P, Tiirola Esa, Providing    improved scheduling request signaling with ACK/NACK or CQI (US    20090100917)-   6. [Patent Document 6]: Li Don, Yang Guang, Multi-channel spread    spectrum system (US 20020015437 A1).

SUMMARY OF THE INVENTION

Embodiments of the present invention are proposed in view of theaforementioned problems in the prior art to remove or alleviate one ormore defects in the related art and at least to provide one advantageouschoice. To achieve the above objectives, the present invention proposesthe following aspects.

Aspect 1. A Reference Signal (RS) generator for generating a RS, whichgenerator comprises a non-correlation sequence generator configured togenerate a non-correlation sequence for RS of a first resource block; afirst spectrum spreading unit configured to spread spectrums of elementsin the non-correlation sequence for RS of the first resource block to bemapped to a first frequency resource of the first resource block, byusing a first group of codes; a second spectrum spreading unitconfigured to spread spectrums of elements in the non-correlationsequence for RS of the first resource block to be mapped to a secondfrequency resource of the first resource block, by using a second groupof Codes; the first and second frequency resources are adjacentfrequency resources in frequency resource elements used for RStransmission in the first resource block, and the first and secondgroups of Codes are mirrors in column to each other; and a mapping unitconfigured to map the elements with their spectrums spread by the firstand second spectrum spreading units to the first and second frequencyresources of the first resource block, respectively. Wherein thefrequency resource is composed of two pairs of consecutive 2 resourceelements on a subcarrier.

Aspect 2. The RS generator according to Aspect 1, wherein the RSgenerator further comprises a third spectrum spreading unit configuredto spread spectrums of elements in the non-correlation sequence for RSof the first resource block to be mapped to a third frequency resource,by using a third group of codes; a fourth spectrum spreading unitconfigured to spread spectrums of elements in the non-correlationsequence for RS of the first resource block to be mapped to a fourthfrequency resource, by using a fourth group of codes; the third andfourth frequency resources are adjacent frequency resources in frequencyresource elements used for RS transmission in the second resource block,and the third and fourth groups of codes are mirrors in column to eachother; wherein the mapping unit further maps the elements with theirspectrums spread by the third and fourth spectrum spreading units to thethird and fourth frequency resources, respectively.

Aspect 3. The RS generator according to Aspect 2, wherein one of thethird and fourth groups of codes is formed by performing a column vectorcyclic shift to one of the first and second groups of codes.

Aspect 4. The RS generator according to Aspect 3, wherein the samecolumn vector has different column serial numbers in the first to fourthgroups of codes.

Aspect 5. The RS generator according to Aspect 1, wherein thenon-correlation sequence generator generates a non-correlation sequencefor RS of a second resource block, frequency resources used for RS ofthe first resource block and frequency resources used for RS of thesecond resource block is adjacent each other; the first spectrumspreading unit spreads spectrums of elements in the non-correlationsequence for RS of the second resource block to be mapped to a firstfrequency resource of the second resource block, by using the firstgroup of codes; the second spectrum spreading unit spreads spectrums ofelements in the non-correlation sequence for RS of the second resourceblock to be mapped to a second frequency resource of the second resourceblock, by using the second group of codes; the first and secondfrequency resources of the second resource block are adjacent frequencyresources in frequency resource elements used for RS transmission in thefirst resource block; the mapping unit further maps the elements in thenon-correlation sequence for RS of the second resource block with theirspectrums spread by the first and second spectrum spreading units to thefirst and second frequency resources of the second resource block,respectively, wherein the first frequency resource of the secondresource block corresponds to the first frequency resource or the secondfrequency resource of the first resource block, and the second frequencyresource of the second resource block corresponds to the secondfrequency resource or the first frequency resource of the firstfrequency block, such that the elements in the non-correlation sequencefor RS of the first resource block and/or the elements in thenon-correlation sequence for RS of the second resource block to bemapped to the adjacent frequency resources in frequency resourceelements used for RS transmission in the first resource block arespectrum-spread by the first group of codes and the second group ofcodes, respectively, in the first resource block and the second resourceblock.

Aspect 6. The RS generator according to Aspect 1, wherein thenon-correlation sequence generator further generates a non-correlationsequence for RS of a second resource block, frequency resources used forRS of the first resource block and frequency resources used for RS ofthe second resource block is adjacent each other; the first spectrumspreading unit spreads spectrums of elements in the non-correlationsequence for RS of the second resource block to be mapped to a firstfrequency resource of the second resource block, by using the thirdgroup of codes; the second spectrum spreading unit spreads spectrums ofelements in the non-correlation sequence for RS of the second resourceblock to be mapped to a second frequency resource of the second resourceblock, by using the fourth group of codes; the first and secondfrequency resources of the second resource block are adjacent frequencyresources in frequency resource elements used for RS transmission in thefirst resource block; the fourth and third groups of codes are mirrorsin column to each other; the mapping unit maps the elements in thenon-correlation sequence for RS of the second resource block with theirspectrums spread by the first and second spectrum spreading units to thefirst and second frequency resources of the second resource block,respectively, wherein the first frequency resource of the secondresource block corresponds to the first frequency resource or the secondfrequency resource of the first resource block, and the second frequencyresource of the second resource block corresponds to the secondfrequency resource or the first frequency resource of the firstfrequency block, such that the elements in the non-correlation sequencefor RS of the first resource block and/or the elements in thenon-correlation sequence for RS of the second resource block to bemapped to the adjacent frequency resources in frequency resourceelements used for RS transmission in the first resource block arespectrum-spread by the first group of codes and the second group ofcodes, respectively, and such that the elements in the non-correlationsequence for RS of the first resource block and/or the elements in thenon-correlation sequence for RS of the second resource block to bemapped to the adjacent frequency resources in frequency resourceelements used for RS transmission in the second resource block arespectrum-spread by the third group of codes and the fourth group ofcodes, respectively, in the first resource block and the second resourceblock; one of the fourth and third groups of codes is formed byperforming a column vector cyclic shift to one of the first and secondgroups of codes.

Aspect 7. The RS generator according to Aspect 6, wherein the samecolumn vector has different column serial numbers in the first to fourthgroups of codes.

Aspect 8. The RS generator according to Aspect 2, wherein thenon-correlation sequence generator generates a non-correlation sequencefor RS of a second resource block, frequency resources used for RS ofthe first resource block and frequency resources used for RS of thesecond resource block is adjacent each other; the first spectrumspreading unit spreads spectrums of elements in the non-correlationsequence for RS of the second resource block to be mapped to a firstfrequency resource of the second resource block, by using a fifth groupof codes; the second spectrum spreading unit spreads spectrums ofelements in the non-correlation sequence for RS of the second resourceblock to be mapped to a second frequency resource of the second resourceblock, by using a sixth group of codes; the first and second frequencyresources of the second resource block are adjacent frequency resourcesin frequency resource elements used for RS transmission in the firstresource block; the sixth and fifth groups of codes are mirrors incolumn to each other; the third spectrum spreading unit spreadsspectrums of elements in the non-correlation sequence for RS of thesecond resource block to be mapped to a third frequency resource of thesecond resource block, by using a seventh group of codes; the fourthspectrum spreading unit spreads spectrums of elements in thenon-correlation sequence for RS of the second resource block to bemapped to a fourth frequency resource of the second resource block, byusing an eighth group of codes; the third and fourth frequency resourcesof the second resource block are adjacent frequency resources infrequency resource elements used for RS transmission in the secondresource block; the seventh and eighth groups of codes are mirrors incolumn to each other; the mapping unit further maps the elements in thenon-correlation sequence for RS of the second resource block with theirspectrums spread by the first to fourth spectrum spreading units to thefirst to fourth frequency resources of the second resource block,respectively.

Aspect 9. The RS generator according to Aspect 8, wherein the samecolumn vector has different column serial numbers in the fifth to eighthgroups of codes; one of the fifth and sixth groups of codes is formed byperforming a column vector cyclic shift to one of the first and secondgroups of codes by a first displacement, and one of the seventh andeighth groups of codes is formed by performing a column vector cyclicshift to one of the first and second groups of codes by a seconddisplacement.

Aspect 10. The RS generator according to Aspect 1, wherein the first andsecond groups of codes are both Walsh code sequences or Fouriertransform sequences.

Aspect 11. A Reference Signal (RS) generation method for generating aRS, which method comprises a non-correlation sequence generating stepfor generating a non-correlation sequence for RS of a first resourceblock; a first spectrum spreading step for spreading spectrums ofelements in the non-correlation sequence for RS of the first resourceblock to be mapped to a first frequency resource of the first resourceblock, by using a first group of codes; a second spectrum spreading stepfor spreading spectrums of elements in the non-correlation sequence forRS of the first resource block to be mapped to a second frequencyresource of the first resource block, by using a second group of codes;the first and second frequency resources are adjacent frequencyresources in frequency resource elements used for RS transmission in thefirst resource block, and the first and second groups of codes aremirrors in column to each other; and a mapping step for mapping theelements with their spectrums spread by the first and second spectrumspreading steps to the first and second frequency resources of the firstresource block, respectively.

Aspect 12. The RS generation method according to Aspect 11, wherein theRS generation method further comprises a third spectrum spreading stepfor spreading spectrums of elements in the non-correlation sequence forRS of the first resource block to be mapped to a third frequencyresource, by using a third group of codes; a fourth spectrum spreadingstep for spreading spectrums of elements in the non-correlation sequencefor RS of the first resource block to be mapped to a fourth frequencyresource, by using a fourth group of codes; the third and fourthfrequency resources are adjacent frequency resources in frequencyresource elements used for RS transmission in the second resource block,and the third and fourth groups of codes are mirrors in column to eachother; wherein the mapping step further maps the elements with theirspectrums spread by the third and fourth spectrum spreading steps to thethird and fourth frequency resources, respectively.

Aspect 13. The RS generation method according to Aspect 12, wherein oneof the third and fourth groups of codes is formed by performing a columnvector cyclic shift to one of the first and second groups of codes.

Aspect 14. The RS generation method according to Aspect 13, wherein thesame column vector has different column serial numbers in the first tofourth groups of codes.

Aspect 15. The RS generation method according to Aspect 11, wherein thenon-correlation sequence generating step generates a non-correlationsequence for RS of a second resource block, frequency resources used forRS of the first resource block and frequency resources used for RS ofthe second resource block is adjacent each other; the first spectrumspreading step spreads spectrums of elements in the non-correlationsequence for RS of the second resource block to be mapped to a firstfrequency resource of the second resource block, by using the firstgroup of codes; the second spectrum spreading step spreads spectrums ofelements in the non-correlation sequence for RS of the second resourceblock to be mapped to a second frequency resource of the second resourceblock, by using the second group of codes; the first and secondfrequency resources of the second resource block are adjacent frequencyresources in frequency resource elements used for RS transmission in thefirst resource block; the mapping step further maps the elements in thenon-correlation sequence for RS of the second resource block with theirspectrums spread by the first and second spectrum spreading steps to thefirst and second frequency resources of the second resource block,respectively, wherein the first frequency resource of the secondresource block corresponds to the first frequency resource or the secondfrequency resource of the first resource block, and the second frequencyresource of the second resource block corresponds to the secondfrequency resource or the first frequency resource of the firstfrequency block, such that the elements in the non-correlation sequencefor RS of the first resource block and/or the elements in thenon-correlation sequence for RS of the second resource block to bemapped to the adjacent frequency resources in frequency resourceelements used for RS transmission in the first resource block arespectrum-spread by the first group of codes and the second group ofcodes, respectively, in the first resource block and the second resourceblock.

Aspect 16. The RS generation method according to Aspect 11, wherein thenon-correlation sequence generating step further generates anon-correlation sequence for RS of a second resource block, frequencyresources used for RS of the first resource block and frequencyresources used for RS of the second resource block is adjacent eachother; the first spectrum spreading step spreads spectrums of elementsin the non-correlation sequence for RS of the second resource block tobe mapped to a first frequency resource of the second resource block, byusing the third group of codes; the second spectrum spreading stepspreads spectrums of elements in the non-correlation sequence for RS ofthe second resource block to be mapped to a second frequency resource ofthe second resource block, by using the fourth group of codes; the firstand second frequency resources of the second resource block are adjacentfrequency resources in frequency resource elements used for RStransmission in the first resource block; the fourth and third groups ofcodes are mirrors in column to each other; the mapping step maps theelements in the non-correlation sequence for RS of the second resourceblock with their spectrums spread by the first and second spectrumspreading steps to the first and second frequency resources of thesecond resource block, respectively, wherein the first frequencyresource of the second resource block corresponds to the first frequencyresource or the second frequency resource of the first resource block,and the second frequency resource of the second resource blockcorresponds to the second frequency resource or the first frequencyresource of the first frequency block, such that the elements in thenon-correlation sequence for RS of the first resource block and/or theelements in the non-correlation sequence for RS of the second resourceblock to be mapped to the adjacent frequency resources in frequencyresource elements used for RS transmission in the first resource blockare spectrum-spread by the first group of codes and the second group ofcodes, respectively, and such that the elements in the non-correlationsequence for RS of the first resource block and/or the elements in thenon-correlation sequence for RS of the second resource block to bemapped to the adjacent frequency resources in frequency resourceelements used for RS transmission in the second resource block arespectrum-spread by the third group of codes and the fourth group ofcodes, respectively, in the first resource block and the second resourceblock; one of the fourth and third groups of codes is formed byperforming a column vector cyclic shift to one of the first and secondgroups of codes.

Aspect 17. The RS generation method according to Aspect 16, wherein thesame column vector has different column serial numbers in the first tofourth groups of codes.

Aspect 18. The RS generation method according to Aspect 12, wherein thenon-correlation sequence generating step generates a non-correlationsequence for RS of a second resource block, frequency resources used forRS of the first resource block and frequency resources used for RS ofthe second resource block is adjacent each other; the first spectrumspreading step spreads spectrums of elements in the non-correlationsequence for RS of the second resource block to be mapped to a firstfrequency resource of the second resource block, by using a fifth groupof codes; the second spectrum spreading step spreads spectrums ofelements in the non-correlation sequence for RS of the second resourceblock to be mapped to a second frequency resource of the second resourceblock, by using a sixth group of codes; the first and second frequencyresources of the second resource block are adjacent frequency resourcesin frequency resource elements used for RS transmission in the firstresource block; the sixth and fifth groups of codes are mirrors incolumn to each other; the third spectrum spreading step spreadsspectrums of elements in the non-correlation sequence for RS of thesecond resource block to be mapped to a third frequency resource of thesecond resource block, by using a seventh group of codes; the fourthspectrum spreading step spreads spectrums of elements in thenon-correlation sequence for RS of the second resource block to bemapped to a fourth frequency resource of the second resource block, byusing an eighth group of codes; the third and fourth frequency resourcesof the second resource block are adjacent frequency resources infrequency resource elements used for RS transmission in the secondresource block; the seventh and eighth groups of codes are mirrors incolumn to each other; the mapping step further maps the elements in thenon-correlation sequence for RS of the second resource block with theirspectrums spread by the first to fourth spectrum spreading steps to thefirst to fourth frequency resources of the second resource block,respectively.

Aspect 19. The RS generation method according to Aspect 18, wherein thesame column vector has different column serial numbers in the fifth toeighth groups of codes; one of the fifth and sixth groups of codes isformed by performing a column vector cyclic shift to one of the firstand second groups of codes by a first displacement, and one of theseventh and eighth groups of codes is formed by performing a columnvector cyclic shift to one of the first and second groups of codes by asecond displacement.

Aspect 20. The RS generation method according to Aspect 11, wherein thefirst and second groups of codes are both Walsh code sequences orFourier transform sequences.

Aspect 21. An code generating apparatus, which comprises a basicorthogonal code acquiring device configured to acquire a group of basicorthogonal codes; a column cyclic shift unit configured to perform acolumn vector cyclic shift to the basic orthogonal codes generated bythe basic orthogonal code acquiring device; and a mirror unit configuredto perform a mirroring in column on the basic orthogonal codes generatedby the basic orthogonal code acquiring device, so as to obtain a firstbasic orthogonal code group pair, and further configured to perform amirroring in column on the basic orthogonal codes having undergone thecyclic shift by the column cyclic shift unit, so as to obtain a secondcode group pair.

Aspect 22. The code generating apparatus according to Aspect 21, whereindisplacement of the column vector cyclic shift is variable.

Aspect 23. The code generating apparatus according to Aspect 21, whereinthe code generating apparatus further comprises a group pair groupacquiring unit configured to control the column cyclic shift unit andthe mirror unit, so as to obtain a group of column serial numberdistinguishable code group pairs where the same column has differentcolumn serial numbers in different code groups.

According to the methods and apparatuses for generating codes proposedin the present invention, RS randomization may be enhanced, the problemof RS power imbalance may be removed, the requirement on orthogonalityat the two dimensions of both the time and frequency may be satisfied,and more robust channel estimation properties may be provided.

With reference to the following description and the drawings, the aboveand further aspects and features of the present invention will come tobe clearer. In the following description and the accompanying drawings,specific embodiments for embodying the invention are disclosed ingreater detail, and modes of execution applicable to the principles ofthe present invention are pointed out. As should be noted, the presentinvention is not restricted in scope thereby. The present inventionincludes various variations, modifications and equalities within thespirits and provisos of the claims attached herewith.

Features described and/or illustrated with respect to one embodiment canbe employed in one or more other embodiments, combined with features ofother embodiments, or replace features of other embodiments in identicalor similar ways.

As should be stressed, the terms of “comprise/include” and“comprising/including”, as used in this disclosure, indicates theexistence of features, integral, steps or component parts, and does notexclude the existence or addition of one or more other features,integral, steps or component parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned as well as other objectives, features and advantagesof the present invention will become more apparent by virtue of thesubsequent description with reference to the drawings, in which:

FIG. 1A is a schematic diagram illustrating a reference signal (RS)generating apparatus according to one embodiment of the presentinvention;

FIG. 1B is a schematic diagram illustrating a RS generating apparatusaccording to one embodiment of the present invention;

FIGS. 2 and 3 illustrate one advantage of the RS generating apparatusaccording to the present invention;

FIG. 4 is a schematic diagram illustrating the flow of generating codegroup pairs by the method according to the present invention;

FIG. 5A is a flow chart illustrating a RS generation method according toone embodiment of the present invention;

FIG. 5B is a schematic diagram illustrating the flow of a RS generationmethod according to another embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating an example of downlink RSresources generated by using the RS generation method according to thepresent invention;

FIG. 7 is a schematic diagram illustrating another example of downlinkRS resources generated by using the RS generation method according tothe present invention;

FIG. 8 is a schematic diagram illustrating power distribution of fourgroups of pre-coded code sequences (column serial number distinguishablecode group pairs) generated according to the present invention mapped tothe first transmission antenna;

FIGS. 9 and 10 illustrate the spectrum spreading treatment of the secondresource block according to one embodiment of the present invention;

FIGS. 11 and 12 illustrate the spectrum spreading treatment of thesecond resource block according to another embodiment of the presentinvention;

FIG. 13 is a schematic diagram illustrating an code generating apparatusaccording to one embodiment of the present invention;

FIG. 14 is a block diagram exemplarily illustrating a computer capableof implementing the method and apparatus according to the embodiments ofthe present invention; and

FIG. 15 is a block diagram exemplarily illustrating the function of atransmitter that employs the RS generating apparatus and generationmethod according to the embodiments of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention are described in greaterdetail below with reference to the drawings. Details and functionsunnecessary to the present invention are not mentioned in thedescription to avoid confused comprehension of the present invention.

FIG. 1A is a schematic diagram illustrating a demodulation referencesignal (DMRS) generating apparatus according to one embodiment of thepresent invention. The DMRS is an example of reference signals (RS) usedfor demodulation. As shown in FIG. 1A, the DMRS generating apparatus 100according to one embodiment of the present invention includes anon-correlation sequence generating unit 101, a first spectrum spreadingunit 102, a second spectrum spreading unit 103 and a mapping unit 104.

The non-correlation sequence generating unit 101 is configured togenerate a non-correlation sequence for RS, which sequence should haveideal correlation (relatively small or even zero). The non-correlationsequence in this context is for instance a Zadoff-Chu sequence or a PNcode sequence. Any methods already known or to be known to personsskilled in the art can be used to generate the non-correlation sequencesuch as the Zadoff-Chu sequence or the PN code sequence, and are notextensively described here. For example, the non-correlation sequencegenerating unit 101 generates a non-correlation sequence (a, c) for acertain resource block.

The first spectrum spreading unit 102 is configured to spread spectrumsof elements (a, for instance) in the non-correlation sequence for RS tobe mapped to a first frequency resource by using a first group of codes,where orthogonal cover codes (OCCs) may be used as the codes.

The second spectrum spreading unit 103 is configured to spread spectrumsof elements (c, for instance) in the non-correlation sequence for RS tobe mapped to a second frequency resource by using a second group ofcodes. The second frequency resource and the first frequency resourceare adjacent frequency resources in frequency resource elements used forRS transmission in the first resource block, and the second group ofcodes and the first group of codes are mirrors in column to each other.The first group of codes and the second group of codes can be referredto as code group pairs.

The mapping unit 104 is configured to map the elements in thenon-correlation sequence for RS with their spectrums spread by the firstand second spectrum spreading units to corresponding frequencyresources, namely to the first and second frequency resources,respectively.

In one embodiment, the first group of codes and the second group ofcodes are Walsh codes. In another embodiment, the first group of codesand the second group of codes are discrete Fourier transform (DFT)sequences. Any other known code sequences may as well be used for thefirst group of codes and the second group of codes. To facilitatedescription, the Walsh codes are only taken as example for description.

FIGS. 2 and 3 illustrate one advantage of the RS generating apparatusaccording to the present invention. When four RS signals are used, asshown in FIG. 2, only one group of codes having a spectrum-spreadinglength of 4 (a, −a, a, −a or c, −c, c, −c) at the time domain is used inthe related art. As shown in FIG. 3, when the DMRS generating apparatusaccording to the embodiment of the present invention is used, it ispossible to map the four RS signals to two subcarriers respectively, soas to reduce the spectrum-spreading length to 2 at the time domain,thereby reducing the requirement on motion speed of the mobile station.

On the other hand, it is also possible to make the power distributionmore uniform, and this will be described below. The present inventiondoes not aim to solve all technical problems existent in the related artin one embodiment, and it is unnecessary to contain all technicaladvantages mentioned in the invention in one embodiment.

Described below is the generation of the code sequences.

FIG. 4 is a schematic diagram illustrating the flow of generating 0° C.group pairs by the method according to the present invention. Altogethereight groups of code sequences are generated in the example illustratedin FIG. 4, each code sequence includes four orthogonal sequences, andeach orthogonal sequence has a length of 4. The code sequences generatedin this illustrated example are Walsh sequences. As should be noted, thenumbers 4 and 8 in this context are used merely for the purpose ofclarity of the description, rather than to restrict the protection scopeof the present invention.

As shown in FIG. 4, the following steps are specifically included.

Step S401—generating a group of code sequence. The circumstanceillustrated in FIG. 4 is represented by a matrix C₁=[C_(1,1); C_(1,2);C_(1,3); C_(1,4)]. This group of code sequence (code group) includesfour orthogonal sequences orthogonal to one another and each having alength of 4:

$C_{1,n} = \begin{matrix}\begin{Bmatrix}{C_{1,n}(1)} \\{C_{1,n}(2)} \\{C_{1,n}(3)}\end{Bmatrix} \\{C_{1,n}(4)}\end{matrix}$

For example, in FIG. 4 there are

$\begin{matrix}{C_{1,1} = \begin{matrix}\begin{Bmatrix}{C_{1,1}(1)} \\{C_{1,1}(2)} \\{C_{1,1}(3)}\end{Bmatrix} \\{C_{1,1}(4)}\end{matrix}} \\{= \begin{matrix}\begin{Bmatrix}1 & \; \\1 & \; \\1 & \;\end{Bmatrix} \\1\end{matrix}}\end{matrix}$ $\begin{matrix}{C_{1,2} = \begin{matrix}\begin{Bmatrix}{C_{1,2}(1)} \\{C_{1,2}(2)} \\{C_{1,2}(3)}\end{Bmatrix} \\{C_{1,2}(4)}\end{matrix}} \\{= \begin{matrix}\begin{Bmatrix}\; & \; \\1 & \; \\1 & \;\end{Bmatrix} \\\begin{matrix}{- 1} \\{- 1}\end{matrix}\end{matrix}}\end{matrix}$and so on so forth.

Step S402—subjecting the group of code sequence C1 to a column mirrortreatment to obtain a new group of code sequence C₂=[C_(2,1); C_(2,2);C_(2,3); C_(2,4)]=[C_(1,4); C_(1,3); C_(1,2); C_(1,1)].

Thus obtained is a pair of code groups (code group pair) used incooperation with each other.

Further, when more cooperatively used pairs of code groups are required,the method can also include the following steps.

Step S403—subjecting the group of orthogonal sequence C₁ to a columnvector cyclic shift treatment to obtain a new group of code sequenceC₃=[C_(3,1); C_(3,2); C_(3,3); C_(3,4)]; and then

Step S404—subjecting the group of code sequence C₃ to a column mirrortreatment to obtain another new group of code sequence C₄=[C_(4,1),C_(4,2); C_(4,3); C_(4,4)].

Cyclic displacement p in the column vector cyclic shift treatment isvariable. For instance, under the circumstance shown in FIG. 4, thecyclic displacement p may be equal to 1, 2 and 3. Accordingly, when morecooperative group pairs are required, Steps S403 and S404 can berepeated for several times, and the cyclic displacement p is varied eachtime.

FIG. 4 illustrates the resultant C₃ and C₄ when p=2. FIG. 4 alsoillustrates the resultant another pair of code groups C₅ and C₆ whenp=3, as well as still another pair of code groups C₇ and C₈ when p=1.

Preferably, when it is required to select two pairs of code groups, thesame column vector of the code sequences can be made different in columnserial numbers in every two pairs of code groups, namely to form a groupof column serial number distinguishable cover code vector group pairs.Taking for example the all-1 column vectors in the illustrated example,it corresponds to the first, the fourth, the third and the secondcolumns in C₁˜C₄, respectively, while corresponds to the fourth, thefirst, the second and the third columns in C₅˜C₈, respectively, and thematrices of these eight groups of code sequences are not equal to oneanother, so that C₁˜C₄ can be used together, and C₅˜C₈ can be usedtogether. The C₁˜C₄ in this context make up a group of column serialnumber distinguishable cover code vector group pairs, and C₅˜C₈ make upa group of column serial number distinguishable cover code vector grouppairs. Likewise, the all-1 column vectors in C₁, C₂, C₇ and C₈ arerespectively in the first, the fourth, the second and the third columns,while the all-1 column vectors in C₃, C₄, C₅ and C₆ are respectively inthe third, the second, the fourth and the first columns, so that C₃, C₄,C₅ and C₆ can be used together, and C₁, C₂, C₇ and C₈ can be usedtogether. C₃, C₄, C₅ and C₆ also make up a group of column serial numberdistinguishable cover code vector group pairs, and C₁, C₂, C₇ and C₈also make up a group of column serial number distinguishable cover codevector group pairs. The advantage in using the groups of column serialnumber distinguishable cover code vector group pairs rests in enablinguniform power distribution on each RS-transmitting frequency resource,and this will be described later.

It is possible to select the groups of column serial numberdistinguishable cover code vector group pairs by a certain method afterall of code group pairs have been obtained, and it is also possible toselect suitable code group pairs and discard unsuitable pairs of codegroups by adding a determining step after performing each round ofcyclic shift to determine whether a group of column serial numberdistinguishable cover code vector group pairs is made up.

In the eight groups of code sequences as generated, vectors formed byelements in each of the pairs of code groups (pairs of code sequencematrix groups) C₁ with C₂, C₃ with C₄, C₅ with C₆ and C₇ with C₈ satisfythe relationship of being orthogonal to one another. Taking C₁ with C₂for example, [C₁₁, C₁₂, C₂₁, C₂₂] are orthogonal to each other, [C₁₃,C₁₄, C₂₃, C₂₄] are also orthogonal, and so on. As can be seen, pairs ofcode groups obtained as thus can achieve orthogonality of the twodimensions of both frequency and time.

FIG. 1B is a schematic diagram illustrating a DMRS generating apparatusaccording to another embodiment of the present invention. As shown inFIG. 1B, the DMRS generating apparatus 100′ according to anotherembodiment of the present invention further includes, in addition to thenon-correlation sequence generating unit 101, the first spectrumspreading unit 102, the second spectrum spreading unit 103 and themapping unit 104 as shown in FIG. 1A, a third spectrum spreading unit105 and a fourth spectrum spreading unit 106.

In the DMRS generating apparatus 100′ according to this embodiment, thenon-correlation sequence generator generates a non-correlation sequencefor RS, for instance a non-correlation sequence (a, b, c, d) for RS.

The first spectrum spreading unit 102 is configured to spread spectrumsof elements (a, for instance) in the non-correlation sequence for RS tobe mapped to a first frequency resource by using a first group of codes(C₁, for instance).

The second spectrum spreading unit 103 is configured to spread spectrumsof elements (c, for instance) in the non-correlation sequence for RS tobe mapped to a second frequency resource by using a second group ofcodes (C₂, for instance). The second frequency resource and the firstfrequency resource are adjacent frequency resources in frequencyresource elements used for RS transmission in the first resource block,and the second group of codes and the first group of codes are mirrorsin column to each other. The first group of codes and the second groupof codes can be referred to as code group pairs. The first group offrequency resource elements used for RS transmission is for instance RSof the first, the second, the fifth and the sixth layers. In thisdisclosure, when it says that both the second frequency resource and thefirst frequency resource are frequency resources in frequency resourceelements used for RS transmission in the first resource block, it meansthat RS carried by the two frequency resources are used for the firstgroup of frequency resource elements used for RS transmission.

The third spectrum spreading unit 105 is configured to spread spectrumsof elements (b, for instance) in the non-correlation sequence for RS tobe mapped to a third frequency resource by using a third group of codes(C₃, for instance).

The fourth spectrum spreading unit 106 is configured to spread spectrumsof elements (d, for instance) in the non-correlation sequence for RS tobe mapped to a fourth frequency resource by using a fourth group ofcodes (C₄, for instance). The third frequency resource and the fourthfrequency resource are adjacent frequency resources in frequencyresource elements used for RS transmission in the second resource block,and the third group of codes and the fourth group of codes are mirrorsin column to each other. In this disclosure, when it says that both thethird frequency resource and the fourth frequency resource are frequencyresources in frequency resource elements used for RS transmission in thesecond resource block, it means that RS carried by the two frequencyresources are used for the second group of frequency resource elementsused for RS transmission. The second group of RS is for instance RS ofthe third, the fourth, the seventh and the eighth layers.

Preferably, the first group of codes and the second group of codes aswell as the third group of codes and the fourth group of codes make upgroups of column serial number distinguishable code group pairs, likethe above-illustrated circumstances in which C₁, C₂ are combined with C₃and C₄. However, this is not necessarily so, as it is also possible tocombine C₁, C₂ with C₆ and C₆, for instance.

FIG. 5A is a flow chart illustrating a DMRS generation method accordingto one embodiment of the present invention.

As shown in FIG. 5A, firstly in Step S501 the non-correlation sequencegenerating unit 101 generates a non-correlation sequence for RS. Thenon-correlation sequence for RS in this context is for instance aZadoff-Chu sequence or a PN code sequence. Any methods already known orto be known to persons skilled in the art can be used to generate thenon-correlation sequence such as the Zadoff-Chu sequence or the PN codesequence, and are not extensively described here.

In Step S502, the first spectrum spreading unit 102 spreads spectrums ofelements in the non-correlation sequence to be mapped to a firstfrequency resource by using a first group of codes.

In Step S503, the second spectrum spreading unit 103 spreads spectrumsof elements in the non-correlation sequence to be mapped to a secondfrequency resource by using a second group of codes. The secondfrequency resource and the first frequency resource are adjacentfrequency resources in the same group of frequency resource elementsused for RS transmission, and the second group of codes and the firstgroup of codes are mirrors in column to each other. The first group ofcodes and the second group of codes can be referred to as code grouppair.

Thereafter in Step S504, the mapping unit 104 maps the elements in thenon-correlation sequence for RS with their spectrums spread by the firstand second spectrum spreading units to corresponding frequencyresources, namely to the first and second frequency resources,respectively.

As easily conceivable, Steps S502 and S503 can be performed eithersuccessively or concurrently.

FIG. 5B is a schematic diagram illustrating a DMRS generation methodaccording to another embodiment of the present invention.

As shown in FIG. 5B, according to the DMRS generation method of anembodiment of the present invention, firstly in Step S501, anon-correlation sequence for RS is generated, which sequence should haveideal correlation (relatively small or even zero). The non-correlationsequence in this context is for instance a Zadoff-Chu sequence or a PNcode sequence.

Then in Step S502, the first spectrum spreading unit spreads spectrumsof elements in the non-correlation sequence for RS to be mapped to afirst frequency resource by using a first group of codes.

In Step S503, the second spectrum spreading unit spreads spectrums ofelements in a plurality of first non-correlation sequences to be mappedto a second frequency resource by using a second group of codes. Thesecond frequency resource and the first frequency resource are adjacentfrequency resources in frequency resource elements used for RStransmission in the first resource block, and the second group of codesand the first group of codes are mirrors in column to each other.

Unlike the DMRS generation method shown in FIG. 5A, the DMRS generationmethod shown in FIG. 5B further includes Steps S505 and S506.

In Step S505, the third spectrum spreading unit spreads spectrums ofelements in the non-correlation sequence for RS to be mapped to a thirdfrequency resource by using a third group of codes.

In Step S506, the fourth spectrum spreading unit spreads spectrums ofelements in the non-correlation sequence for RS to be mapped to a fourthfrequency resource by using a fourth group of codes. The fourthfrequency resource and the third frequency resource are adjacentfrequency resources in frequency resource elements used for RStransmission in the second resource block, and the fourth group of codesand the third group of codes are mirrors in column to each other.

And preferably, the groups of group pairs formed by the fourth group ofcodes and the third group of codes as well as by the first group ofcodes and the second group of codes make up groups of column serialnumber distinguishable code group pairs.

In Step S504, the mapping unit 104 maps the elements in thenon-correlation sequence for RS with their spectrums spread by the firstto fourth spectrum spreading units to corresponding frequency resources,namely to the first to fourth frequency resources, respectively.

As easily conceivable, Steps S502, S503, S505 and S506 can be performedeither successively or concurrently.

FIG. 6 is a schematic diagram illustrating an example of downlink DMRSresources generated by using the DMRS generation method according to thepresent invention.

FIG. 6 illustrates a circumstance in which there are two layers. Assumethat the RSs occupy twelve subcarriers (also referred to as “resourceelements”, RE) in physical resource blocks (PRB) of the sixth andseventh OFDM symbols and the thirteenth and fourteenth OFDM symbols ineach subframe of the LTE-A system. The RSs of the first and secondlayers occupy the same PRB, and are differentiated via codes each havinga length of 2.

Under such a circumstance, after the non-correlation sequence for RS(such as a, b, c) is generated, the first group of codes is used tospread spectrums of elements (a, for instance) in the non-correlationsequence for RS to be mapped to a first subcarrier in frequency resourceelements used for RS transmission in the first resource block (RS of thefirst and second layers), the second group of codes is used to spreadspectrums of elements (b, for instance) in the non-correlation sequencefor RS to be mapped to a sixth subcarrier (which is also in frequencyresource elements used for RS transmission in the first resource block),and the first group of codes is used to spread spectrums of elements (c,for instance) in the non-correlation sequence for RS to be mapped to aneleventh subcarrier (which is also in frequency resource elements usedfor RS transmission in the first resource block). Mapping is performedthereafter.

The first group of codes and the second group of codes are mirrors incolumn to each other, that is, they form a pair of code groups.

In this context, although the first, the sixth and the eleventhsubcarriers as exemplarily illustrated are not physically adjacent,because they are in frequency resource elements used for RS transmissionassociated with the same layers, they are adjacent insofar as they arein frequency resource elements used for RS transmission associated withthe same layers, so they are referred to as adjacent frequency resourcesin frequency resource elements used for RS transmission in the firstresource block.

FIG. 7 is a schematic diagram illustrating another example of downlinkRS resources generated by using the RS generation method according tothe present invention.

FIG. 7 illustrates a circumstance in which there are four layers. Assumethat the RSs occupy twenty-four subcarriers (also referred to as“resource elements”, RE) in physical resource blocks (PRB) of the sixthand seventh OFDM symbols and the thirteenth and fourteenth OFDM symbolsin each subframe of the LTE-A system. The RSs of the first and secondlayers occupy the same PRB, and are differentiated via codes each havinga length of 2. The RSs of the third and fourth layers occupy the samePRB, and are differentiated via codes each having a length of 2.

Under such a circumstance, after the non-correlation sequence for RS isgenerated, the first group of codes (C₁, for instance) is used to spreadspectrums of elements in the non-correlation sequence for RS to bemapped to a 0^(th) subcarrier with respect to the first and secondlayers, the second group of codes (C₂, for instance) is used to spreadspectrums of elements in the non-correlation sequence for RS to bemapped to a fifth subcarrier with respect to the first and secondlayers, and the first group of codes is used to spread spectrums ofelements in the non-correlation sequence for RS to be mapped to a tenthsubcarrier with respect to the first and second layers. The third groupof codes (C₃, for instance) is used to spread spectrums of elements inthe non-correlation sequence for RS to be mapped to a first subcarrierwith respect to the third and fourth layers, the fourth group of codes(C₄, for instance) is used to spread spectrums of elements in thenon-correlation sequence for RS to be mapped to a sixth subcarrier withrespect to the third and fourth layers, and the third group of codes isused to spread spectrums of elements in the non-correlation sequence forRS to be mapped to an eleventh subcarrier with respect to the third andfourth layers. Mapping is performed thereafter.

The first group of codes and the second group of codes are mirrors incolumn to each other, that is, they form a pair of code groups. Thethird group of codes and the fourth group of codes are mirrors in columnto each other, that is, they also form a pair of code groups. The firstand second layers can be differentiated from the third and fourth layersin the form of FDM, that is, they are differentiated by frequencies.

As should be noted, the pair of code groups formed by the first group ofcodes and the second group of codes can either be identical with ordifferent from the pair of code groups formed by the third group ofcodes and the fourth group of codes.

When there are more than four layers, the method can also be carried outin the similar way as shown in FIG. 7. That is to say, frequencyresources that carry RS are divided into two groups with respect todifferent layers, and elements in the non-correlation sequence for RSmapped to each of the groups are spectrum-spread by different groups ofcodes. Different groups are differentiated by frequencies.

For instance, also in the pattern of RS resources illustrated in FIG. 7,after the non-correlation sequence for RS is generated, the first groupof codes is used to spread spectrums of elements in the non-correlationsequence for RS to be mapped to the 0^(th) subcarrier with respect tothe first to fourth layers, the second group of codes is used to spreadspectrums of elements in the non-correlation sequence for RS to bemapped to the fifth subcarrier with respect to the first to fourthlayers, and the first group of codes is used to spread spectrums ofelements in the non-correlation sequence for RS to be mapped to thetenth subcarrier with respect to the first to fourth layers. The thirdgroup of codes is used to spread spectrums of elements in thenon-correlation sequence for RS to be mapped to the first subcarrierwith respect to the fifth to eighth layers, the fourth group of codes isused to spread spectrums of elements in the non-correlation sequence forRS to be mapped to the sixth subcarrier with respect to the fifth toeighth layers, and the third group of codes is used to spread spectrumsof elements in the non-correlation sequence for RS to be mapped to theeleventh subcarrier with respect to the fifth to eighth layers. Mappingis performed thereafter.

The first group of codes and the second group of codes are mirrors incolumn to each other, that is, they form a pair of code groups. Thethird group of codes and the fourth group of codes are mirrors in columnto each other, that is, they also form a pair of code groups. The firstto fourth layers can be differentiated from the fifth and eighth layersin the form of FDM, that is, they are differentiated by frequencies. Atthis time, the length of the codes should be 4.

As should be noted under such a circumstance, the pair of code groupsformed by the first group of codes and the second group of codes caneither be identical with or different from the pair of code groupsformed by the third group of codes and the fourth group of codes.However, groups of column serial number distinguishable code group pairsare preferably used. The first to fourth layers make up the first groupof frequency resource elements used for RS transmission, and the fifthto eighth layers make up the second group of frequency resource elementsused for RS transmission. But the above is merely taken as examples, asthe first group of frequency resource elements used for RS transmissionmay as well be frequency resource elements used for RS transmission ofthe first, the second, the fifth and the sixth layers, and the secondgroup of frequency resource elements used for RS transmission may aswell be frequency resource elements used for RS transmission of thethird, the fourth, the seventh and the eighth layers.

As can be seen from FIG. 6 and FIG. 7, the code sequences arespectrum-spread at the time domain, that is, RSs corresponding to thesame subcarrier on the sixth, the seventh, the thirteenth and thefourteenth OFDM symbols constitute spectrum-spread codes each having alength of 4. Moreover, RSs corresponding to the k^(th) and the k+6^(th)subcarriers on the sixth, the seventh, the thirteenth and the fourteenthOFDM symbols also constitute spectrum-spread codes each having a lengthof 4; that is to say, orthogonality is provided in the two dimensions oftime and frequency.

FIG. 8 is a schematic diagram illustrating power distribution of fourgroups of pre-coded code sequences (groups of column serial numberdistinguishable code group pairs) generated according to the presentinvention mapped to the first transmission antenna. As can be seen fromFIG. 8, if the row vectors in the pre-coding matrices are all 1, aftercolumn vectors of the four groups of code sequence matrices C₁˜C₄ arerespectively multiplied with and added to the row vectors of thepre-coding matrices, RSs corresponding to the sixth, the seventh, thethirteenth and the fourteenth OFDM symbols are respectively 4a, 0, 0, 0on the k^(th) subcarrier; RSs corresponding to the sixth, the seventh,the thirteenth and the fourteenth OFDM symbols are respectively 0, 0,4c, 0 on the k−1^(th) subcarrier; RSs corresponding to the sixth, theseventh, the thirteenth and the fourteenth OFDM symbols are respectively0, 0, 0, 4d on the k−6^(th) subcarrier; and RSs corresponding to thesixth, the seventh, the thirteenth and the fourteenth OFDM symbols arerespectively 0, 4b, 0, 0 on the k−7^(th) subcarrier. As it is notdifficult to see, power of the RSs is uniformly distributed on the fourOFDM symbols, and the problem of power imbalance is avoided.

FIGS. 9 and 10 illustrate the spectrum spreading treatment of the secondresource block according to one embodiment of the present invention.

According to one embodiment of the present invention, as shown in FIGS.9 and 10, as for an adjacent resource block (the second resource blockin FIGS. 9 and 10, for instance), demodulation reference signals can begenerated by the same mode as the original resource block (the firstresource block in FIGS. 9 and 10, for instance); moreover, the groups ofcodes as applied between the two resource blocks are made to be mirrorsin column to each other with respect to the adjacent frequency resourcesof RS transmission for the same layers, namely to form a pair of codegroups. For instance, as shown in FIG. 10, with respect to the tenthsubcarrier of the first resource block and the 0^(th) subcarrier of thesecond resource block, the groups of codes C1 and C2 as mirrors incolumn to each other are used; with respect to the eleventh subcarrierof the first resource block and the first subcarrier of the secondresource block, the groups of codes C3 and C4 as mirrors in column toeach other are used. For further instance, as shown in FIG. 9, withrespect to the eleventh subcarrier of the first resource block and thefirst subcarrier of the second resource block, the groups of codes C1and C2 as mirrors in column to each other are used.

As should be noted, as shown in FIGS. 9 and 10, the first frequencyresource and the second frequency resource may indicate differentsubcarriers at different resource blocks.

FIGS. 11 and 12 illustrate the spectrum spreading treatment of thesecond resource block according to another embodiment of the presentinvention.

According to another embodiment of the present invention, as shown inFIGS. 11 and 12, with respect to adjacent resource blocks, two groups ofcodes as mirrors in column to each other are used. As shown in FIG. 11,different pairs of code groups are used in the second resource block forfrequency resources (the first, the sixth and the eleventh subcarriersin the second resource block, for instance) corresponding to thefrequency resources (the first, the sixth and the eleventh subcarriersin the first resource block, for instance) in the original resourceblock. Preferably, the two pairs of code groups form a group of columnserial number distinguishable code group pairs. For further instance asshown in FIG. 12, different pairs of code groups are used in the secondresource block for frequency resources corresponding to the frequencyresources in the original resource block. The pairs of code groups usedin the adjacent resource block also form a group of column serial numberdistinguishable code group pairs. One group of codes in the group ofcolumn serial number distinguishable code group pairs used in the secondresource block is obtained by performing column vector cyclic shift onone group of codes in the group of column serial number distinguishablecode group pairs used in the first resource block.

FIG. 13 is a schematic diagram illustrating an code generating apparatusaccording to one embodiment of the present invention.

As shown in FIG. 13, the code generating apparatus according to thepresent invention includes a basic orthogonal code acquiring unit 1301,a mirror unit 1302, a column cyclic shift unit 1303 and a group pairgroup acquiring unit 1304.

The basic orthogonal code acquiring unit 1301 is configured to acquire agroup of basic orthogonal codes, such as the Walsh codes or DFT codes aspreviously mentioned.

The column cyclic shift unit 1303 is configured to perform a columnvector cyclic shift to the basic orthogonal codes generated by the basicorthogonal code acquiring unit 1301. Displacement of the column vectorcyclic shift is variable.

The mirror unit 1302 is configured to perform a mirroring in column onthe basic orthogonal codes generated by the basic orthogonal codeacquiring unit 1301, so as to obtain a first basic orthogonal code grouppair, and further to perform a mirroring in column on the basicorthogonal codes having undergone the cyclic shift by the column cyclicshift unit 1303, so as to obtain a second, a third, or more code grouppairs.

The group pair group acquiring unit 1304 is configured to control thecolumn cyclic shift unit 1303 and the mirror unit 1302, so as to obtaina group of column serial number distinguishable code group pairs.

As should be noted, the group pair group acquiring unit 1304 can bedispensed with in certain applications.

Under certain circumstances, the column cyclic shift unit 1303 can alsobe dispensed with.

Various constituent modules, units and subunits in the above apparatusmay be configured through software, firmware, hardware or combinationsthereof. The specific configuring means or manners are well known by aperson skilled in the art, and herein are not repeated. In case of theimplementation through software or firmware, programs constructing thesoftware shall be installed from a storage medium or network to acomputer with dedicated hardware structure (e.g., a general computer asillustrated in FIG. 14), and the computer can perform various functionswhen being installed with various programs.

FIG. 14 is a block diagram illustrating a computer capable ofimplementing the method and apparatus according to the embodiments ofthe present invention.

In FIG. 14, a Central Processing Unit (CPU) 1401 performs variousprocessing according to programs stored in a Read Only Memory (ROM) 1402or programs loaded from a storage section 1408 to a Random Access Memory(RAM) 1403. Data required by the CPU 1401 to perform various processingshall be stored in the RAM 1403 as necessary. The CPU 1401, the ROM 1402and the RAM 1403 are connected to each other via a bus 1404. AnInput/Output (I/O) interface 1405 may also be connected to the bus 1404as necessary.

As necessary, the following components may be connected to the I/Ointerface 1405: an input section 1406 (including keypad, mouse, etc.),an output section 1407 (including display such as Cathode-Ray Tube (CRT)and Liquid Crystal Display (LCD), and loudspeaker, etc.), a storagesection 1408 (including hard disk, etc.) and a communication section1409 (including network interface card such as LAN card, modem, etc.).The communication section 1409 for example performs a communicationprocessing through a network such as Internet. A driver 1410 may also beconnected to the I/O interface 1405 as necessary. A detachable medium1411 such as magnetic disk, optical disk, magneto-optical disk,semiconductor memory, etc. may be mounted on the driver 1410 asnecessary, so that the computer program read therefrom will be installedinto the storage section 1408 upon request.

In case the above series of processing is implemented through software,programs constructing the software shall be installed from a networksuch as the Internet or a storage medium such as the detachable medium1411.

A person skilled in the art shall appreciate that the storage medium isnot limited to the detachable medium 1411 as illustrated in FIG. 14which stores programs and is distributed independently from the deviceto provide the programs to the subscriber. The detachable medium 1411for example includes magnetic disk (including floppy disk (registeredtrademark)), compact disk (including Compact Disk Read Only Memory(CD-ROM) and Digital Versatile Disk (DVD)), magnetic optical disk(including Mini Disk (MD) (registered trademark)) and semiconductormemory. Or the storage medium may be the ROM 1402, the hard disk in thestorage section 1408, etc. in which programs are stored and distributedto the subscriber together with the device containing them.

The present invention further provides a program product that storesmachine readable instruction codes capable of executing the above methodaccording to the embodiments of the present invention when being readand executed by a machine.

Accordingly, a storage medium for loading the program product thatstores the machine readable instruction codes is also included in thedisclosure of the present invention. The storage medium includes, but isnot limited to, floppy disk, optical disk, magneto-optical disk, memorycard, memory stick, etc.

FIG. 15 is a block diagram exemplarily illustrating the function of atransmitter that employs the RS generating apparatus and generationmethod according to the embodiments of the present invention. A powersource, a storage unit, a data generating module and the like which arenot of direct relevance to understanding the technical solution ofpresent invention are omitted in this block diagram.

As shown in FIG. 15, data is encoded as to channels at a channelencoding unit 1501, and is then modulated at a modulating unit 1502. Themodulated data is mapped as to resources at a resource mapping unit1503. At the same time, RSs are generated by a RS generating unit 1506by using the RS generating apparatus or generation method according tothe present invention and are mapped. As should be noted, in the abovedescription the RS generating apparatus also has a mapping unit, whichis actually the same one as the resource mapping unit 1503, that is tosay, data and RSs are mapped at the same time. Thereafter, the datamapped to a physical channel is pre-coded at a pre-coding unit 1504,receives OFDM modulation at an OFDM modulating unit 1505, and is thensent out via an antenna.

Description of the present invention is given for purposes ofexemplification and illustration, and is not exhaustive or restrictiveof the present invention within the form disclosed herein. Manymodifications and variations are apparent to persons ordinarily skilledin the art. The selection and description of the embodiments aredirected to better explanation of the principles and practicalapplications of the present invention, and to enabling personsordinarily skilled in the art to so comprehend the present invention asto design various embodiments with various modifications adapted toparticular purposes of use.

What is claimed is:
 1. A transmitter, comprising: a reference signalgenerator configured to generate a reference signal, wherein thereference signal generator comprises: a sequence generator configured togenerate a sequence for reference signal of a first resource block; afirst spectrum spreading unit configured to spread spectrums of elementsin the sequence for reference signal of the first resource block to bemapped to a first frequency resource of the first resource block, byusing a first group of codes; a second spectrum spreading unitconfigured to spread spectrums of elements in the sequence for referencesignal of the first resource block to be mapped to a second frequencyresource of the first resource block, by using a second group of codes;the first and second frequency resources are adjacent frequencyresources in frequency resource elements used for reference signaltransmission in the first resource block, and the first and secondgroups of codes are mirrors in column to each other; a third spectrumspreading unit configured to spread spectrums of elements of in thesequence for reference signal of the first resource block to be mappedto a third frequency resource of the first resource block, by using athird group of codes; a fourth spectrum spreading unit configured tospread spectrums of elements in the sequence for reference signal of thefirst resource block to be mapped to a fourth frequency resource of thefirst resource block, by using a fourth group of codes; the third andfourth frequency resources are adjacent frequency resources in frequencyresource elements used for reference signal transmission in the firstresource block, and the third and fourth groups of codes are mirrors incolumn to each other; and a mapping unit configured to map the elementswith their spectrums spread by the first and second spectrum spreadingunits to the first and second frequency resources of the first resourceblock, respectively, and map the elements with their spectrums spread bythe third and fourth spectrum spreading units to the third and fourthfrequency resources of the first resource block, respectively.
 2. Thetransmitter according to claim 1, wherein one of the third and fourthgroups of codes is formed by performing a column vector cyclic shift toone of the first and second groups of codes, and the same column vectorhas different column serial numbers in the first to fourth groups ofcodes.
 3. A communication system, comprising: a transmitter thattransmits a reference signal; and a receiver that receives the referencesignal transmitted from the transmitter, wherein the transmitterincludes a reference signal generator configured to generate thereference signal which comprises: a sequence generator configured togenerate a sequence for reference signal of a first resource block; afirst spectrum spreading unit configured to spread spectrums of elementsin the sequence for reference signal of the first resource block to bemapped to a first frequency resource of the first resource block, byusing a first group of codes; a second spectrum spreading unitconfigured to spread spectrums of elements in the sequence for referencesignal of the first resource block to be mapped to a second frequencyresource of the first resource block, by using a second group of codes;the first and second frequency resources are adjacent frequencyresources in frequency resource elements used for reference signaltransmission in the first resource block, and the first and secondgroups of codes are mirrors in column to each other; a third spectrumspreading unit configured to spread spectrums of elements of in thesequence for reference signal of the first resource block to be mappedto a third frequency resource of the first resource block, by using athird group of codes; a fourth spectrum spreading unit configured tospread spectrums of elements in the sequence for reference signal of thefirst resource block to be mapped to a fourth frequency resource of thefirst resource block, by using a fourth group of codes; the third andfourth frequency resources are adjacent frequency resources in frequencyresource elements used for reference signal transmission in the firstresource block, and the third and fourth groups of codes are mirrors incolumn to each other; and a mapping unit configured to map the elementswith their spectrums spread by the first and second spectrum spreadingunits to the first and second frequency resources of the first resourceblock, respectively, and map the elements with their spectrums spread bythe third and fourth spectrum spreading units to the third and fourthfrequency resources of the first resource block, respectively.
 4. Amethod for transmitting a reference signal, comprising: a sequencegenerating step for generating a sequence for reference signal of afirst resource block; a first spectrum spreading step for spreadingspectrums of elements in the sequence for reference signal of the firstresource block to be mapped to a first frequency resource of the firstresource block, by using a first group of codes; a second spectrumspreading step for spreading spectrums of elements in the sequence forreference signal of the first resource block to be mapped to a secondfrequency resource of the first resource block, by using a second groupof codes; the first and second frequency resources are adjacentfrequency resources in frequency resource elements used for referencesignal transmission in the first resource block, and the first andsecond groups of codes are mirrors in column to each other; a thirdspectrum spreading step for spreading spectrums of elements of in thesequence for reference signal of the first resource block to be mappedto a third frequency resource of the first resource block, by using athird group of codes; a fourth spectrum spreading step for spreadingspectrums of elements in the sequence for reference signal of the firstresource block to be mapped to a fourth frequency resource of the firstresource block, by using a fourth group of codes; the third and fourthfrequency resources are adjacent frequency resources in frequencyresource elements used for reference signal transmission in the firstresource block, and the third and fourth groups of codes are mirrors incolumn to each other; a mapping step for mapping the elements with theirspectrums spread by the first and second spectrum spreading units to thefirst and second frequency resources of the first resource block,respectively, and map the elements with their spectrums spread by thethird and fourth spectrum spreading units to the third and fourthfrequency resources of the first resource block, respectively; and atransmitting step for transmitting the generated reference signal to areceiver.